The present invention relates to an improved filter mouthpiece for a smoking article, such as a cigarette, in particular a filter mouthpiece having a hollow tube extending axially therethrough from one end towards, but not as far as, the other end, and to a cigarette provided with such a mouthpiece.
In a conventional cigarette, the resistance to draw and air ventilation, if any, of the combined tobacco rod and filter mouthpiece stay substantially the same throughout the smoking of the cigarette. This has the effect of increasing the dry particulate matter (DPM) delivery with successive puffs. Particularly, although not solely, in the case of low delivery cigarettes, so-called "low-tar cigarettes", this may be undesirable, since the first puff may be rather weak in taste and "impact" and, anyway, the taste and "impact" of the cigarette to the smoker will change as the cigarette is smoked.
It is known to vary the resistance to draw (RTD) of a cigarette by providing a filter mouthpiece having a hollow tube extending from the tobacco end thereof toward, but ending short of, the mouth end. When a cigarette provided with such a mouthpiece is smoked, smoke passes along the tube toward the mouth end and impinges on the filter material at the mouth end of the tube. Components of the smoke condense on the filter material adjacent the open mouth end of the tube, blocking the tube and causing at least some of the smoke to pass through the surrounding filter material, so increasing the resistance to draw of the cigarette. This has the effect of evening out to some extent the DPM delivery as smoking progresses.
It is also known to provide a tube having small slits along its length. This increases the resistance to draw the filter mouthpiece more gradually and results in more even DPM delivery than if a completely impervious tube is used. However, this arrangement still provides a cigarette in which the DPM delivery increases as the cigarette is smoked.